1. Field of the Invention
The present invention relates to a pulverizer which performs, for example, micron-order pulverization, and more particularly to a pulverizer having a classifying mechanism incorporating a pulverization zone and a classification zone.
2. Description of the Prior Art
Referring to FIG. 1, there is shown a conventional pulverizer of this type. A disk 82 is mounted to a first rotary shaft 80 attached in a frame 90. A rotary hammer 83 protruding upward is provided at a peripheral end of the disk 82. A liner 84 is mounted to the inner surface of the frame 90 so as to face the rotary hammer 83. Air admitted through a air supplying hole 91 provided at a lower part of the frame 90 goes upward as shown by the arrows. Materials are supplied into the frame 90 through a screw feeder 92.
Reference numeral 85 represents a guide ring. The outside space of the guide ring 85 serves as the pulverization zone for pulverizing materials and the inside thereof serves as the classification zone for classifying the pulverized materials according to the particle diameter and weight. In the classification zone, a classifying fan 86 attached to a second rotary shaft 81 is provided.
The material supplied by the screw feeder 92 is pulverized between the rotary hammer 83 and the liner 84. Then, it goes up in the pulverization zone together with the air and enters the classification zone at the upper end thereof. The material having entered the classification zone is classified into the one to be discharged to an exit 93 and the one to be dropped along the guide ring 85 to enter the pulverization zone again. The material pulverized into a predetermined diameter or smaller is discharged to the exit 93 and directed to a dust collector (not shown) through a passage connecting with the exit.
In the pulverizer thus arranged, the liner 84 has concaves and convexes on its inner surface as shown in FIGS. 2B and 3B in any prior art. However, the configuration of the hammer 83 is different. Specifically, in the prior art (Japanese Published Patent Application S50-21695) of FIGS. 2A and 2B, the hammer 83 is provided on the disk 82 with a gap and its surface which faces the liner 84 has neither concaves nor convexes.
In the prior art (Japanese Patent Application H5-259552) of FIGS. 3A and 3B, the hammer 83 has concaves and convexes on its outer surface. In the cases of FIGS. 2A and 2B and 3A and 3B, the material not discharged to the exit 93 by the classifying fan 86 passes between the hammer 83 and the hammer 83 to circulate.
As another prior art, the one (Japanese Published Patent Application S61-36463) shown in FIGS. 4A and 4B is known. In this prior art, the hammer 83 has concaves and convexes on its entire periphery. The hammer 83 and the liner 84 are formed to be longer in the vertical direction and the pulverization of the supplied material is performed by passing it through the pulverization zone once. Therefore, there is no circulation zone.
In the prior art of FIGS. 2A and 2B, the pulverizing capability is weak since the hammer 83 has neither concaves nor convexes. For this reason, it takes a long time to pulverize the material into a predetermined particle diameter. In the prior art of FIGS. 3A and 3B, since the hammer 83 has a pulverizing tooth provided with concaves and convexes, the number of collisions between the material and the hammer 83 increases and the pulverizing power is improved accordingly. However, since the hammer 83 is not provided on the entire periphery, the improvement of the pulverizing power is limited and the pulverizing efficiency is not improved so much.
Since the prior art of FIGS. 4A and 4B has no idea of circulating the material to pulverize it and pulverizes the material only by passing it through the pulverizing zone once, to sufficiently increase the pulverizing power, it is necessary to form the hammer 83 and the liner 84 to be sufficiently long in the vertical direction, so that the rotational power (i.e. the torque of the motor) of the hammer 83 is remarkably high.
Furthermore, since the material which cannot be pulverized into a predetermined particle diameter or smaller is also discharged, the material which cannot be classified by the succeeding classifier is wasted or necessarily fed back to an entrance 91 of the pulverizer through another passage.